The long term objective of this research project is to understand how the neural circuits in the mammalian retina encode the visual scene for transmission to the rest of the brain. Specifically, we focus on the interneurons in the parallel pathways from photoreceptors to ganglion cells, as they establish the first stages of visual processing. Our detailed knowledge of the anatomy of these neural circuits in the retina has already provided us with strong clues about their function, and we are now poised to address how each cell's synapses and each cell's intrinsic conductances shape incoming visual signals. The proposed research addresses questions, such as, when are specific synapses active, and when are they silent? Does the primary role of a synapse change depending on conditions? Do voltage dependent conductances affect a cell's output? Experiments designed to answer these questions will be performed using single and dual whole cell patch clamp recording of identified neurons in in vitro slice preparations of rabbit retina. Specific Aim 1 addresses specific hypotheses about the roles of the different rod pathways and how each pathway, whether operating alone or in parallel with another, shapes the light responses of cone bipolar cells. Specific Aim 2 examines the reciprocal synapses between All amacrine cells and OFF cone bipolars and the reasonable hypothesis of interaction of ON and OFF pathways through their connections with the All amacrine cell. Specific Aim 3 defines the functional significance of regenerative potentials and voltage gated conductances in ON cone bipolar cells in terms of their influence on the light response of individual cells and networks of cells coupled by gap junctions.